Internal combustion engine



P. J. ANDREWS INTERNAL COMBUSTION ENGINE Filed March 26, 1956 Aug. 6, 1957 United States Patent() 2,801,622 `INTERNAL COMBUSTION ENGINE Percy I. Andrews, Warwick, R. I.

Application March 26, 1956, Serial No. 573,758

2 Claims. (Cl. 12S-78) The present invention relates to automotive engines, and has particular reference to a novel piston arrangement therefor.

The principal object of the invention is to provide a piston construction which stores up energy during the combustion stroke, and releases the stored up energy during the power stroke.

Another object of the invention is to provide a piston construction which provides a more complete scavenging action.

A further object of the invention is to utilize a double piston having an intermediate energy absorbing and dispensing cushion of air.

An additional object of the invention is to provide a double piston which has a positive scavenging piston movement during the latter half of the exhaust stroke.

Still another object of the instant invention is the provision of a piston construction which enables prolonged combustion to take place, thereby resulting in increased power.

With the above and other objects and advantageous features in view, the invention consis-ts of a novel arrangement of parts more fully disclosed in the detailed description following, in conjunction with the accompanying drawings, and more specifically defined in the claims appended thereto.

In the drawings which illustrate the best mode presently contemplated by me for carrying out my invention:

Fig. 1 is a vertical sectional view of an engine embodying the invention;

Fig. 2 is a sectional elevation of the parts in suction position;

Fig. 3 is a sectional elevation ofthe parts in compressed position;

Fig. 4 is a sectional elevation of the parts in power position; and

Fig. 5 is a sectional elevation of the parts in exhaust position.

It has been found desirable to provide a piston arrangement which stores up explosive energy at ignition, then releases the stored-up energy during the power stroke, and is then positively moved to scavenge the cylinder. To this end, I provide a shell piston and skirt piston, 'an -air cushion being maintained between the two pistons, whereby at ignition a rapid expansion of the combustion chamber is possible, thus permitting more complete burning of the gas. At the same time, this rapid expansion causes a compression of the air cushion, which compression acts as an additional drive force during the power stroke and further as means for accomplishing a highly rapid and complete exhaust thereby resulting in a relatively cool running engine.

Referring now to the drawings, the cylinder is of any standard type, with a cylinder head 12 which preferably has recessed inlet and exhaust valves 14 and 16 operated in the usual manner from the engine crankshaft 18. A shell piston is slidably mounted in the piston cylinder 10, and has `an annular ring flange 22 mounted #latentecl Aug. 6, 1957.

in an internal groove 24 adjacent the lower end thereof. A skirt piston 26 of standard type is slidably mounted in the shell piston, and has a spring pressed check valve 28 in the upper surface 30 thereof to maintain an air cushion 32 between the two pistons, the lower edge Y34 of the skirt being adapted to` engage thevv shell flange 22 for imparting downward movement to the shell piston. A connecting rod 36 connects the skirt piston to the crankshaft 18.

A partition 38 extends across the shell piston in par-'l allcl relation to the piston top 40 and preferably encloses approximately one-third of the shell piston internal area. As will be apparent from Fig. l, the skirt piston height is `approximately one-third that of the shell piston. Conventional rings 42 and 44 may be provided in the shell piston and skirt piston, respectively, it being noted that the shell piston rings 42 are specifically located above partition 38. This is important since it insures that there will be no wear due to friction on the inside of piston 20 at the point where the rings are located, which wear could conceivably cause cracking of the piston due to the reduced thickness of the piston Wall.

In operation, the skirt piston compresses the air cushion 32 during the compression stroke whereby to push the shell piston upwardly. When ignition occurs, the explosion immediately forces the shell piston downwardly against the `action of air cushion 32 whereby to provide an expansion chamber which enables complete combustion of the gas to take place. Continued expansion of the burning gas forces the shell piston downwardly to rotate the crankshaft while at the same time the compressed air cushion 32 also `aids in impar-ting power for effecting crankshaft rotation.

Immediately at the termination of the power stroke and upon initiation of the exhaust stroke, the compressed air cushion 32 will push the shell piston upwardly until flange 22 engages the bottom of the skirt piston, and the pistons remain in this relative position throughout the entire exhaust and suction strokes.. This rapid upward movement of the shell piston until contact is made with the skirt piston imparts impetus to the upward movement of the latter, thereby aiding in the rotation of the crankshaft during the exhaust stroke, and thus resulting in a more rapid exhaust, and hence a relatively cool running engine. It will further be seen that due to the presence of the relatively movable pistons, a substantially complete scavenging of the cylinder is accomplished due to the fact that the shell piston is lifted by air cushion 32 to substantially completely clear the cylinder, thus resulting in improved engine operation. The air space between the shell piston top and the partition functions as additional means to keep the engine relatively cool in that it acts as a heat insulation area.

It will be obvious that the check valve 28 functions to insure that suliicient air will always be present to provide the necessary air cushion 32 and Will prevent undesirable escape of air when the cushion is under compression. Should air inadvertently be lost from the air cushion when the latter is under compression, however, valve 28 will permit replenishment thereof during the exhaust and suction strokes.

Although l have disclosed specific constructional features embodying the invention, it is obvious that changes in the size, shape and arrangement of the parts may be made to suit dilferent automotive engine designs, without departing from the spirit and the scope of the invention as defined in the appended claims.

I claim:

l. A compound pistonfor internal combustion engines and the like comprising a shell piston, a partitionin spaced relation to the upper end thereof and forming an air pocket therewith which functions as a heat insulation area, a vskirt lpiston slidably positioned in said shell piston beneathsaid'partitiom whereby an air cushion is provided between thepartition and the skirt piston top, inwardly extending means yat the shell piston lower end engageable by the lower end yof the skirt piston, means for impaiting lreciprocal motion 'to said skirt piston, valve means in said skirt piston top for admitting replenishing air to the air cushion, and a plurality of it piston rings circumferentially surrounding said shell piston in the (intel-surface thereof, said rings being located above said partition.

2. In thedevice of claim 1, said partition being located so as' to enclose approximately one-third of the shell piston area, vand said skirt 'piston height being `approximately one-third that of the shell piston.

References Cited in the le of this patent UNITED STATES PATENTS 312,494 Nash Feb. 17, 1885 1,444,423 Miller Feb. 6, 1923 1,876,917 Gosslau Sept. 13, 1932 1,926,598 Peterson Sept. 12, 1933 

